JP2013183374A - Oscillator and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To match a modulation signal with a piezoelectric transducer even when the resonance frequency of the piezoelectric transducer fluctuates.SOLUTION: An oscillator includes: a piezoelectric transducer 300; a drive signal generation unit 100 for generating a drive signal to be inputted to the piezoelectric transducer 300; and an adjustment unit 200 provided between the drive signal generation unit 100 and the piezoelectric transducer 300, and capable of adjusting electrical immittance. The resonance frequency of the piezoelectric transducer 300 is frequently deviated from a design value due to the fluctuation during manufacturing. Therefore, even though the frequency of the drive signal is matched with the resonance frequency of the piezoelectric transducer 300 in designing, actually, the frequency of the drive signal is often deviated from the resonance frequency of the piezoelectric transducer 300. Use of the adjustment unit 200 capable of adjusting the electrical immittance allows the drive signal generation unit 100 and the piezoelectric transducer 300 to be matched with each other.

Description

  The present invention relates to an oscillation device and a method for manufacturing the oscillation device.

  One of the speakers is a parametric speaker. The parametric speaker modulates an audio signal into a modulation signal in an ultrasonic band, and demodulates the modulation signal into an audible sound in the atmosphere. A piezoelectric vibrator is often used as a vibration source of a parametric speaker.

  On the other hand, Patent Document 1 describes that the number of turns of a transformer is adjusted so that the resonance frequency of a circuit composed of an electrostatic ultrasonic transducer and a transformer matches the driving frequency of the electrostatic ultrasonic transducer. ing.

JP 2007-174619 A

  In order to increase the output of the parametric speaker, it is desirable to make the frequency of the modulation signal coincide with the resonance frequency of the piezoelectric vibrator. However, the resonance frequency of the piezoelectric vibrator often deviates from the design value due to variations in manufacturing. In this case, the output of the parametric speaker is lowered.

  An object of the present invention is to provide a transmitting device and a method of manufacturing an oscillating device that can match a modulation signal and a piezoelectric vibrator even if the resonance frequency of the piezoelectric vibrator varies.

According to the present invention, a piezoelectric vibrator;
Drive signal generating means for generating a drive signal input to the piezoelectric vibrator;
An adjusting means provided between the drive signal generating means and the piezoelectric vibrator, and capable of adjusting an electrical immittance;
An oscillation device is provided.

According to the present invention, the step of inspecting the characteristics of the piezoelectric vibrator and adjusting the electrical immittance of the adjusting means based on the inspection result;
Providing the adjusted adjusting means between the piezoelectric vibrator and a driving signal generating means for generating a driving signal input to the piezoelectric vibrator;
A method for manufacturing an oscillation device comprising:

  According to the present invention, the modulation signal and the piezoelectric vibrator can be matched even if the resonance frequency of the piezoelectric vibrator varies.

It is a block diagram which shows the function structure of the oscillation apparatus which concerns on 1st Embodiment. The 1st example of the adjustment part is shown. The 2nd example of the adjustment part is shown. It is a figure which shows the structure of a piezoelectric vibrator. It is a flowchart which shows the manufacturing method of an oscillation apparatus. It is a figure for demonstrating the process performed by step S20 of FIG. It is a figure which shows the function structure of the oscillation apparatus which concerns on 2nd Embodiment. It is a top view which shows the layout of a piezoelectric vibrator.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

(First embodiment)
FIG. 1 is a block diagram illustrating a functional configuration of the oscillation device according to the first embodiment. The oscillation device according to the present embodiment includes a piezoelectric vibrator 300, a drive signal generation unit 100, and an adjustment unit 200. The drive signal generation unit 100 generates a drive signal input to the piezoelectric vibrator 300. The adjustment unit 200 is provided between the drive signal generation unit 100 and the piezoelectric vibrator 300, and adjusts the electrical immittance so that the Q value of the piezoelectric vibrator 300 is within ± 20% of a predetermined value. Can be adjusted in range.

  The resonance frequency of the piezoelectric vibrator 300 often deviates from the design value due to variations in manufacturing. For this reason, even if the frequency of the drive signal and the resonance frequency of the piezoelectric vibrator 300 coincide with each other at the time of design, the frequency of the drive signal and the resonance frequency of the piezoelectric vibrator 300 often deviate in practice. In contrast, in the present embodiment, the adjustment unit 200 can adjust the Q value of the piezoelectric vibrator 300 within a range of ± 20% from a predetermined value by adjusting the electrical immittance. For this reason, by using the adjustment unit 200, the piezoelectric vibrator 300 can be matched with the frequency of the drive signal. Details will be described below.

  The drive signal generation unit 100 converts an audio signal input from the outside into a modulation signal for a parametric speaker. The modulation method here is AM (Amplitude Modulation) modulation, DSB (Double Side Band) modulation, SSB (Single Side Band) modulation, or FM (Frequency Modulation) modulation. The piezoelectric vibrator 300 oscillates a modulation wave based on the modulation signal. This modulated wave is demodulated into audible sound in the atmosphere.

  FIG. 2 shows a first example of the adjustment unit 200. The adjustment unit 200 has a plurality of resistors 202 connected in parallel to each other. And the adjustment part 200 adjusts the resistance value as an electrical immittance by cutting off some of the resistors 202. In the example shown in this figure, the second resistor 202 from the top is cut and has a cutting portion 204. Here, the resistance values of the resistors 202 may be equal to each other or different from each other.

  FIG. 3 shows a second example of the adjustment unit 200. The adjustment unit 200 has a variable resistor 212. The electrical immittance is adjusted by adjusting the resistance value of the variable resistor 212.

  FIG. 4 is a diagram illustrating the configuration of the piezoelectric vibrator 300. The piezoelectric vibrator 300 includes a piezoelectric element 302, a vibration member 304, and a holding member 306.

  The piezoelectric element 302 is attached to one surface of the vibration member 304, and is formed of piezoelectric ceramics such as PZT, for example. However, the piezoelectric element 302 may be formed of other piezoelectric materials. The planar shape of the piezoelectric element 302 is smaller than the planar shape of the vibration member 304.

  The vibration member 304 has a sheet shape and vibrates due to vibration generated from the piezoelectric element 302. The vibration member 304 adjusts the fundamental resonance frequency of the piezoelectric element 302. The thickness of the vibration member 304 is preferably 5 μm or more and 500 μm or less. In addition, the vibration member 304 preferably has a longitudinal elastic modulus, which is an index indicating rigidity, of 1 GPa or more and 500 GPa or less. When the rigidity of the vibration member 304 is too low or too high, there is a possibility that the characteristics and reliability of the mechanical vibrator are impaired. The material constituting the vibration member 304 is not particularly limited as long as it is a material having a high elastic modulus with respect to the piezoelectric element 302 that is a brittle material, such as metal or resin, but phosphor bronze or the like from the viewpoint of workability and cost. Stainless steel or the like is preferable.

  The holding member 306 supports the edge of the vibration member 304.

  FIG. 5 is a flowchart showing a method for manufacturing the oscillation device according to the present embodiment. The process shown in this figure is performed every time one oscillator is manufactured.

  First, the characteristics of the piezoelectric vibrator 300 are inspected, and the electrical characteristics of the piezoelectric vibrator 300 are calculated (step S10). Next, using this electrical characteristic, a coefficient to be set in the adjustment unit 200 is calculated (step S20). Details of the processing performed here will be described later. Next, the adjustment of the electrical immittance of the adjustment unit 200 is performed (step S30). For example, when the adjustment unit 200 has the structure shown in FIG. 2, the resistor 202 to be cut is determined, and the resistor 202 is cut using a laser or the like. When the adjustment unit 200 has the structure shown in FIG. 3, the resistance value of the variable resistor 212 is determined. Thereafter, an oscillation device is assembled using the drive signal generation unit 100, the adjustment unit 200, and the piezoelectric vibrator 300 (step S40).

FIG. 6 is a diagram for explaining the process performed in step S20 of FIG. This figure shows an equivalent circuit of the piezoelectric vibrator 300. The electrical immittance of the piezoelectric vibrator 300 is configured by an inductance L _m , a resistance R _m , a capacity C _m , and a static capacity C _d as dynamic immittance. The mechanical quality factor Q of the piezoelectric vibrator 300 is calculated by the following equation (1).
Q = (ω × L _m ) / R _m (1)

Here, ω is a resonance frequency and is represented by the following equation (2).
ω = 1 / √ (L _m × C _m ) (2)

From the equation (1), if the target Q is Q _{targ and} the resistance of the adjustment unit 200 necessary for this is R _targ , Q _targ is expressed by the following equation (3).
Q _targ = (ω × L _m ) / (R _m + R _targ ) (3)

From the equation (3), R _targ is expressed by the following equation (4).
R _targ = (ω × L _m ) / Q _targ −R _m (4)

Therefore, by substituting the value measured in step S10 of FIG. 5 into the equation (4), the coefficient of the adjustment unit 200, that is, R _targ is calculated. When the adjustment unit 200 has the configuration shown in FIG. 2, the resistor 202 to be cut is determined so that the resistance value of the adjustment unit 200 is closest to R _targ .

As described above, according to the present embodiment, even if the resonance frequency of the piezoelectric vibrator varies, the Q value of the piezoelectric vibrator 300 is adjusted to within ± 20% from the predetermined value by adjusting the electrical immittance of the adjusting unit 200. It can be adjusted within the range. For this reason, even if the frequency of the drive signal and the resonance frequency of the piezoelectric vibrator 300 vary, the drive signal generation unit 100 and the piezoelectric vibrator 300 can be matched. According to the equation (3), the adjusting unit 200 may not be the resistance value but may be an inductor whose inductance L _targ can be adjusted, or a capacitor whose capacitance value can be adjusted. .

(Second Embodiment)
FIG. 7 is a diagram illustrating a functional configuration of the oscillation device according to the second embodiment. The present embodiment has the same configuration as that of the oscillation device according to the first embodiment except for the following points.

  First, the oscillation device has a plurality of piezoelectric vibrators 300. The plurality of piezoelectric vibrators 300 are arranged in a matrix as shown in FIG.

  The adjustment unit 200 is provided for each of the plurality of piezoelectric vibrators 300. Each adjustment unit 200 performs the process shown in FIG. 5 according to the characteristics of the piezoelectric vibrator 300 corresponding to the adjustment unit 200. For this reason, the electrical immittance of the piezoelectric vibrator 300 after being adjusted by the adjusting unit 200 varies to some extent. The range of this variation is ± 20% with respect to the average value.

  The drive signal generation unit 100 includes a decoding unit 110, an upsampling unit 120, a modulation signal generation unit 126, a D / A conversion unit 128, and an amplification unit 130. Among these, the upsampling unit 120 and the modulation signal generation unit 126 are configured by, for example, a DSP (digital signal processor).

  In the present embodiment, the signal input to the oscillation device is a digital signal, which is an audio signal compressed by a predetermined method (for example, MP3 (MPEG (Moving Picture Experts Group) Audio Layer-3)). The decoding unit 110 decodes this audio signal. The decoding unit 110 is, for example, a CPU (Central Processing Unit).

  The upsampling unit 120 upsamples the audio signal input from the decoding unit 110. The sampling frequency of the audio signal needs to be somewhat higher than the carrier wave. The audio signal input from the decoding unit 110 is often sampled at a rate of 48 kHz or less. When the carrier wave of the modulation signal generated by the modulation signal generator 126 is 40 kHz or higher, the sampling frequency of the audio signal needs to be 96 kHz or higher, for example. The upsampling unit 120 upsamples the audio signal to, for example, 96 kHz or 192 kHz. The frequency of the audio signal after upsampling by the upsampling unit 120 is appropriately selected according to the frequency of the carrier wave of the modulation signal generated by the modulation signal generation unit 126.

  The modulation signal generation unit 126 modulates the audio signal after the upsampling by the upsampling unit 120 into an ultrasonic band signal, and generates a modulation signal for a parametric speaker. The modulation method here is the same as in the first embodiment. Note that the modulation signal generated by the modulation signal generation unit 126 is a digital signal.

  The D / A conversion unit 128 converts the modulation signal output from the modulation signal generation unit 126 into an analog signal. The amplification unit 130 amplifies the analog modulation signal output from the D / A conversion unit 128 and inputs the amplified modulation signal to the piezoelectric vibrator 300 via the adjustment unit 200.

  Also according to this embodiment, the same effect as that of the first implementation device can be obtained. Further, the characteristics of the plurality of piezoelectric vibrators 300 can be made uniform.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

DESCRIPTION OF SYMBOLS 100 Drive signal generation part 110 Decoding part 120 Upsampling part 126 Modulation signal generation part 128 D / A conversion part 130 Amplification part 200 Adjustment part 202 Resistance 204 Cutting part 212 Variable resistance 300 Piezoelectric vibrator 302 Piezoelectric element 304 Vibration member 306 Holding member

Claims (6)

A piezoelectric vibrator;
Drive signal generating means for generating a drive signal input to the piezoelectric vibrator;
An adjusting means provided between the drive signal generating means and the piezoelectric vibrator, and capable of adjusting an electrical immittance;
An oscillation device comprising: The oscillation device according to claim 1,
A plurality of the piezoelectric vibrators;
The drive signal generation means inputs the drive signal to the plurality of piezoelectric vibrators,
The adjusting means is provided for each of the plurality of piezoelectric vibrators,
The oscillation device in which the electrical immittance of the piezoelectric vibrator after being adjusted by the adjusting means varies within a range of ± 20% with respect to the average value. The oscillation device according to claim 1,
The adjusting means has a plurality of resistors connected in parallel to each other,
An oscillation device in which a part of the plurality of resistors is cut. The oscillation device according to claim 1 or 2,
An oscillation device in which the adjusting means has a variable resistor. In the oscillating device according to any one of claims 1 to 4,
The drive signal generating means is an oscillation device that generates a modulation signal as a parametric speaker as the drive signal. Inspecting the characteristics of the piezoelectric vibrator, and adjusting the electrical immittance of the adjusting means based on the inspection result;
Providing the adjusted adjusting means between the piezoelectric vibrator and a driving signal generating means for generating a driving signal input to the piezoelectric vibrator;
A method of manufacturing an oscillation device comprising:

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